Fluid transfer mechanism



y 1944' M. CASERTA 2,353,545 FLUID TRANSFER MECHANISM I Filed June 12,1941 Z Sheets-She et l Patented July 11, 1944 FLUID TRANSFERMII'ICHAINTISM Michele Caserta, Detroit, Mich, assignor to ThompsonProducts Incorporated, Clevelam, Ohio, a corporation 01' OhioApplication June 12, 1941, Serial No. 397,763 11 Claims. (01. 277-45)This invention relates to fluid transfer mechanism and moreparticularly, although not so restricted, to the type used in aircraftfuel transfer installations.

Usually in such installations a pump, driven for instance by the engine,transfers the gasoline or other fuel from the reservoir to thecarburetor or other distributing device; one of the objects of thepresent invention is to keep a constant fuel pressure at the carburetoreven if variations take place in the speed at which the pump is driven,or in the pressure of the fuel at the pump inlet side, or in theatmospheric pressure, or in the fuel flow, or in any other factortending to affect the fuel pressure.

Another object is to provide means by which fluid may be bypassed fromthe inlet side to the outlet side with a minimum pressure drop, as isdesirable for instance in the event that the pump should be out of orderand an emergency pump be used.

A further object is to provide control means which are free in theirmovements without tendencyto stick or bind, so as to respond to theslightest variation in pressure and as a consequence control saidpressure within very close limits.

Still a further object of the present invention is to provide amechanism which is simple, compact, light, easily manufactured andassembled, and generally efficient.

These and other objects will be more apparent from the followingdescription and from the accompanying drawings.

Figures 1, 2, and 3 are an end view, a side elevational view, and a planview respectively of a fuel pump embodying the present invention, Figure3 showing also semi-diagrammatically partly in section a fragment of amounting flange to which said pump may be attached, and some of themounting bolts.

Figure 4 is an elevational view of the flange end only of said pump.

Figure 5 is a. cross sectional view taken substantially on line 55 ofFigure 2, some of the parts being left not-sectioned for clearn'ess ofillustration.

Figure 6 is a similar cross sect onal view taken substantially on line6-43 of Figure 5.

Figure 7 is a semi-diagrammatical fragmentary view showing partly insection and partly in elevation an alternate construction of the valve.Q Figure 8 is a semi-'diagrammatical fragmentary sectional view of analternative diaphragm mounting structure.

Figure 9 is an elevational view of a modified form of bearing, and

Figure 10 is a sectional view of said bearing taken on line ID of Figure9.

In the figures the fuel pump assembly is indicated by the numeral l0 andincludes a pump housing II, a valve housing l2, and a cover i3.

Pump housing II is provided with a bore M, terminated by an end wall orthrust face i5. In said bore M are lodged in line and preferably pressfitted a thrust bearing IS, a flrst journal bearing ii, an eccentricpump chamber or liner l8, and a. second journal bearing IS. A pin 26prevents the rotation of parts it to Hi relative to each other andrelative to housing I I, while pin 2| prevents the relative rotation ofchamber l8 and bearing i9.

A straight cylindrical rotor 22 is supported in bearings l1 and I9, andis provided at one end with a splined hole 23 through which it may bedriven, and with four radial slots 24, through which the vanes 25 slide.

A ring or pump gasket 26, preferably made of resilient or deformablematerial such as for instance synthetic rubber, is pressed againstbearing l9 by the bevel end 21 of gland 28 which is assembled to theflange 29 of pump housing H by means of screws 30 (Figures 2 and i). Theparts are preferably so proportioned that when the screws 30 aretightened, bearings i5 and i1, liner I8 and bearing I9 are all pressedagainst the end wall I5 and seal ring 26 is compressed. and preferablydeformed to produce a fluid. tight seal between bore l4 and gland 2B,and so prevent the passage of fluid from the pump side 3| of gland 28 tothe other or outer side 32 along said bore; excessive squeezing of thepump seal ring 26 is prevented by gland flange 33 which comes in contactwith flange 29.

When the whole pump assembly is assembled to the mounting flange 34 bymeans of the usual bolts 35 and nuts 36, the heads of screws 30 arecovered by said flange 34 and .the additional powerful action of nuts 36holds together flanges 33 and 29. It is then clearly apparent that by mystructure I avoid the use of large threaded bodies such as used in somestructures in which a large gland is threaded into a housing, and notonly I avoid the danger of seizure of such large threads particularly ifthe parts are made of aluminum, but avoid the expensive tools andoperations necessary for such threads, and at assembly completelyexclude the human element as a factor in the tightness and compressionof the pump seal. Furthermore'I dont need to make screws 30 veryaccurate or strong, nor do I need to lock them, as they are relied upononly to hold the parts together during storage and transit, while whenthe pump is in operation all the parts are securely held by the usuallypowerful studs 35 and nuts 36. On the other hand to disassemble my pumpascrew driver is the only tool needed to loosen the screws 30, afterwhich the gland, shaft, and related parts slip out of the pump housingand fall apart one from the other.

Gland 28 is provided with a land 31 which holds it in central positionrelative to bore I4, andwith a concentric land 38 which is useful inmounting the pump assembly centrally on for instance the mounting flange84 usually provided for it on the engine.

In its central portion gland 28 is also provided with an inner flange 39and recessed seat 40, with four radially spaced openings 4I preferablycored out in casting so as to leave four pillars 42, and with a secondinner flange 43. A ring or gasket 49 of soft or resilient material suchfor instance as synthetic rubber, is lodged in recessed seat 40 andsupports centrally and squarely with the bore a seal seat -I preferablymade of wear resistant material such as bronze.

Shaft 5| is provided with two splined ends, one, 52, for driving therotor-22, and the other, 53, for connection to the pump driving means;the shaft is also provided with a flange 54 which is pressed againstseal seat 50 by means of spring 55, and with a second flange 56substantially in line with flange 43 with which it forms a wall of aprotection of the inside of the pump' from foreign matter. It is clearthat the rubber gasket 49 is helpful in taking care of misalignment between shaft and gland or mounting flange, and

by its resiliency allows the seal seat 50 to follow flange 54 in itspossibly wabbly movement, and so effectively prevents leaks past saidseat.

Spring 55 at the other end presses against rofor 22, which in turn restsagainst thrust bearing it.

Pump housing II is provided with two cavities or openings and GIsymmetrically opposite with reference to the rotor, and with two ports82 and 03 connected thereto respectievly. The pump will operate ineither direction but for the purpose of simplicity of description wewill assume that it be operating in anticlockwise direction, as shown byarrows 04 in Figure 5;

then cavity and port 62 will be on the inlet' or low pressure side, andcavity GI and port 63 will be on the outlet or high pressure side.

Valve housing I Z and valve cover I3 are fastened to pump housing II bymeans of screws 85, which are preferably located in plan view accordingto a pattern symmetrical with reference to the pump. axis, so that thevalve housing can be inverted or rotated 180 when the pump is operatedin clockwise direction.

Valve housing I? is provided with an outlet or pressure side openingor-chamber 68 which communicates with the outlet port 03 of the pump,

and which for simplicity of description will also be called lowerchamber; and with an inlet or suction side opening or chamber 61 whichcommunicates with the inlet port 82 and which will also be called upperchamber, with the understanding, however, that the expressions upper andlower do not in any manner define or limit the relative location of saidchambers to each other or to the pump housing.

Said chambers are separated by a partition or wall 68 which is providedwith a port or valve seat 89, which may be closed by relief valve I0.The lower part of relief valve I0 terminates in a cylindrical portion Hwhich is guided in bore 12 provided in the lower wall 13 of valvehousing I 2, while the upper part I5 is also cylindri- "cal and isguided in bore I8.

The upper surface 11 of pump housing II, bore 12, and valve lower walllI confine a space pletes the horizontal wall of elements 68, 80, 82,

and 83 which close communication between upper and lower chambers.

Numerals 85 and 88 indicate ribs castin valve housing I2 to stiffen thestructure and promote smoother flow of the fluid therethrough.

The relief valve I0 is provided with upper Iatcral ports 89 and lowerlateral ports I00, and bypass valve seat 82 is provided with lateralports IOI and axial port I02.

A diaphragm I03 is held in fluid tight manner at its outer edge betweenvalve housing I2 and cover I3, and rests in its central portion againstby-pass valve seat 82. On diaphragm I03 we find a washer I04 providedwith a seat I05 for ball I06, which in turn is held. at its upper sidein seat I01 provided in spring washer I08-. Said washer I08 carries'onits locating seat I09 the adjusting spring IIO which at its upper endrests on seat III of adjusting washer II2"into which the adjusting screwI I 3 is threaded. It. will be noted in Figures 5 and 6 that washer I08is preferably of larger diameter than washer I04, so that if theassembly of washer I08 and washer. I04 with the centering ball betweenthem were accidentally displaced laterally, washer I08 would touch theinside of cover I3 but washer I04 would still remain free. The samefigures also show a rib I50 with which cover I3 is preferably providedin correspondence with washer I08 to prevent excessive accidentallateral displacement of said washer at assembly or in operation.

Valve cover I3 is formed with a bore H4 and a counterbore or seat H5.Adjusting screw II3 is provided with a flange I I6 which rests incounterbore II 5, and with an upper threaded stem I I! which fits intobore H4 and may be clamped tight to cover I3 by means of check nut H8,or may be rotated for instance by means of screw driver slot H9.

Valve cover I3 is provided onthe inside with a vertical groove E20 inwhich a finger iii of washer H2 can slide up and down while at the sametime preventing said washer IIZ from rotating. When adjusting screw titis turned, said finger prevents washer H2 from rotating and theconsequent action of threaded hole I 22 in the center of washer H2compels said washer to move up and down and so adjust the spring tensionas desired.

An important advantage of this construction is that flange III; ofadjusting screw H3 is.

pressed against its seat H5 at all times by the tension of spring 0 andtherefore is prevented from accidental rotation by the, friction and hasno tendency to lose its adjustment even if check nut H8 is left loose;'furthermore said flange pressed on its seat provides a fluid tightclosure,

the effectiveness of which is only increased by the application ofsupercharger pressure above the diaphragm for instance through port I23.

It will be seen that as rotor 22 and vanes 24 rotate in the directionindicated by arrow 64, the fluid is carried from .inlet or low pressureport 5 to outlet or high pressure port 8|, and if the 2,353,545, freeflow thereafter is impeded, pressure is built and the fluid flowsbetween seat 68 and valve and through port 61 back to the inlet side andto openings 62 and 60. a

Should there be any tendency for the fluid pressure to pulsate, andtherefore for valve 70 to vibrate or bounce on and off its seat, it willbe seen that the lower part II of said valve will 'act as a piston incylinder 12 and trap fluid in chamber I8, so that a dash-pot action willbe obtained'and the vibrations of minimized.

Should it be desirable to pump fluid from port to port 6| by meansindependent from the pump proper, for instance when the pump is out oforder or when the engine is not turning, the fluid from. inlet ports 60and 62 will pass through ports 61, 09, IOI, I02, will lower valve disc83 against the tension of spring 84, and through ports I00, 66, and 63will reach outlet port 6I. It is clear that disc 83 may be made verylight and thin, and of light material such as Bakelite; said disc 83 isnormally pressed against its seat 82 by the fluid pressure on the outletside, so that spring 84 may be very light, and the drop of pressure offluid by-passed through the valve will be very small.

It is a known fact that it is very difllcult to produce springs whoseends will stay naturally parallel when free and when under tension;usually, as the spring is compressed its ends tend to twist out ofparallel and form an angle, and the direction of the spring action doesnot remain axial. In other words it may be said that if one end is heldstationary and the other one is compressed,said other one will tend torotate as it moves axially, and the spring will give a valve 10 will betorque component besides the expected axial reaction component.

This is an important factor in bringing about stickiness in valves thatare spring pressed, as the torque component will twist the valvesideways against its guiding means, and the valve will stick and bind.The present invention provides means whereby any spring tendency totwist spends itself freely and no binding action is transmitted to thevalve.

In fact, if the lower face of spring H0 had any tendency to twist orrotate it can freely do so, as it rests on washer I00 which can freelyrotate around ball I06, which in turn transmits only an axial componentto washer I04 which, through diaphragm I03 and valve 82 presses on valveI0.

It will be noted that the adjusting screw I I3 is held or guided on thevertical axis of the pump and valve assembly by bore H4 and counterboreH5, and in turn hold and guides on said axis the adjusting washer H2which in turn through shoulder III guides spring H0; the lower end ofspring H0 rests around shoulder I09 and centers washer I08, while ballI06 resting in seats I0'I and I05 centers washer I08 .and I04, so thatwasher. I04 is finally held on the axis of the valve assembly withouthaving any lateral guides which might introduce friction and bindingaction. In conclusion, there is nothing in the valve assemblyconstructed in accordance with the present invention that can producebinding action, and the result, confirmed in practice, is that saidvalve is extremel free in its movement and gives very sensitive pressurecontrol.

While the spring and washers are held in line as just described, it ispreferable to have washer I08 not much smaller than the inside of coverI3 or otherwise loosely guided in cover I3 to avoid that by error orbecause of excessive curvature of the axis of the spring said washerI08, 'at assembly be mounted too far off the axis of the valve, or thatit be jarred off said axis by accident during operation. The rib I50,although not essential, washer I08.

The structure described will give best results if the spring I I0 is ofrather large diameter in proportion to its length, so it will restsquarely at both ends and keeps the parts in line at assembly. i

The valve seat, the diaphragm, and the related parts are preferably soproportioned that the effective area of the diaphragm equals theeffective area of the relief valve, so that variations in the fuelpressure at the inlet side will have no influence on the pressureregulation; furthermore, if pressure is applied to the upper side of thediaphragm for instance by means of the engine supercharger and throughport I23, the result will be the same as if said pressure were applieddirectly on the top of the relief valve, namely the outlet pressureadjustment will be increased in direct proportion to the superchargerpressure applied.

It will be noted that diaphragm I03 is preferably made of resilient andeasily compressible facilitates the centering of material such forinstance as synthetic rubber:

the shoulder, groove, or free space I24 left between valve housing I 2and cover I3 is preferably, made slightly narrower than the diaphragmthickness, so that when the whole assembly is tightened together bymeans of screws the diaphragm -remains clamped all around at itsperiphery in a fluid tight manner, and fills at least in part circulargroove I25 and chamfer space I26 forming undulations or rings which arebeneficial in insuringfluid tightness even in the event that thediaphragm material should take a permanent set.

I'll

An alternative construction of the diphragm is shown in Figure 8 and maybe preferable when the diaphragm I2! is made of thinand not verycompressible material; accordingly, a ring I28 of easily compressiblematerial is inserted in groove I24 with the diaphragm and, being thickerthan the groove when free, supplies the necessary pressure to provide afluid tight joint when all parts are clamped together and bulges somewhat into grooves I25 and chamfer space I26.

In valves provided with diaphragms as known in the art we usually findbolts that go through the diaphragm and washers and nuts to fastenrodsor similar parts to the diaphragm and pick up its action; holes in thediaphragm material, and the squeezing action of the bolts and washersare a continuous source of trouble, as the holes are a good start fordiaphragm cracks and the nuts or clamping meansare often assembledtooloose and produce a leak, or too tight and squeeze and break thediaphragm, which again 1 leaks as a result. Other known structuresresort phragm is usually preferable, but other-mes 'of diaphragms orbellows or equivalent pressure responsive means known in the art couldbe subthe spirit of the lifted by the outlet pressure, the springpressure keeps the diaphragmtightly held between washer I04 and valve82, and said diaphragm transmits its action upwards against spring H ordownwards against valve 82 and on to valve III as the case may be.

In a similar manner the by-pass valve seat 82 is pressed in afluid-tight manner against relief valve by spring IIO without the use offurther fastening means. I The result of this construction is that whenthe four screws 65 that hold the valve assembly together are released,all the valves and related parts come apart, and then they may beassembled together again with equal ease and without the use of anytools.

It can be noted that fuel pressures used at present in aircraftinstallations are mostly in the rangeof 3-20 lbs. per square inch, andas a consequence if the relief valve area is for instance one and .ahalf square inches, spring IIO shall.

II. on the other hand, must be slightly longer than the vanes and thechamber, to allow free a movement of the vanes even if there are slightvariations in manufacture and assembly. As a consequence, andparticularly. with rotors of the preferred straightv cylindrical type asshown in the figures, the vanes are allowed a small amount of end playas indicated in exaggerated scale at numeral I40 in Figure 6. While inmost angular positions the vanes are located endwise by the faces Illand It! of bearings I1 and I9 respectively, in the sealing zone I43(Figure 5), where the rotor and chamber are practically in contact, saidfaces disappear and the vanes are free to move endwise to the end of theslots. Then, by continuing to rotate, the vanes pass the sealing zoneand begin to emerge from the rotor and hit the inside surface of thebearing, thereby often spoiling said bearing.

To avoid this action I preferably modify my bearings as indicated inFigures :5 and 10, by providing at each side of the sealing zone I aramp or cam surface recess I starting from the sealing zone with depthpreferably equal to the slot end clearance I40 and zero width, and thengradually decreasing in depth and increasing in be adjusted to a tensionof approximatelyiafi to 30 pounds. On the other hand, by-pass spring 84is preferably made as light as possible, and since it is assisted by theoutlet pressure in keeping valve disc 83 closed, it is usually made juststrong enough to hold disc 83 up to valve 82 against gravity andvibrations; the ratio of tension between spring III! and spring 84 maythen be said to be of the order of 400:1 to 3000:1, and the action ofspring 84 in tending to lift valve 82 from valve Ill and incounteracting the tension of spring IIIl maybe disregarded.

'In the modified form shown in Figure '7, the

, relief valve and the by-pass valve seat are all in one piece I30 whichstill includes a vertical or axial port I3l which communicates with theupper valve housing chamber 61 through a row of radial ports I32 andwith the lower chamber 66 through a row of radial ports I33; verticalport I3I is provided with a by-pass valve seat or opening I33 againstwhich the by-pass valve disc 83 is pressed by spring I35, thus closingcommunication between the upper and lower rows of radial ports.

Below the lower row of ports I33 is another annular seat I36, againstwhich a washer or disc I31 is pressed by spring I38, which at its lowerend rests on pump housing II. As the tension of spring I38 is preferablymade greater than the tension of spring I35, disc I3'I will remainpressed against its seat I 36, and so effectively close the lower end ofvalve I30, which then will collaborate with valve housing bore 12 inproviding a dash-pot action to minimize any tendency of valve I30 tovibrate or bounce up and down.

No claim is made in the present application to any particular type ofbore in pump chamber l8, or to any particular type of vanes operabletherein, many being known in the art.v It is slightly shorter than thelength of chamber I8,

so as to avoid loss of fluid from the high pressure to the low pressureside between the vane ends and the faces of the bearings. The rotorslots width, until it blends with the face I." of the bearing.

The start ll! of the cam surface I is preferably located within thesealing zone, the width of which may vary according to the particulartype of bore adopted, and in some cases may be reduced to onegeneratrix; the end or blending line I48 of the cam surface with th faceof the bearing I takes place preferably within that part of the bearingthat is always open to the inlet or outlet port and in which no actualpumping occurs; the shape of the cam surface as indicated inFlgure 9 ispreferably made to follow somewhat the shape of the chamber bore and alittle wider to allow some'clearance at the vane tips.

It will be apparent that as the rotor rotates,

each vane upon reaching the sealing zone is free to move endwise and getinside the bearing; as it' emerges from the sealing zone and begins toprotrude from the rotor it meets the cam surface I, which graduallybrings it back to its central position in the slot. As the cam recessaffects only sections of the hearing which are in communication witheither the inlet or the outlet port anyhow, no loss of .efliciency ofthe pump takes place, while less accuracy is needed in the manufactureof the rotor and its slots.

What I claim is:

1. In a valve assembly, a valve housing having coaxial cylindrical boresand an intermediate annular partition providing a valve seat, a valvefor said seat having guiding portions at all times in contact with saidbores and having an axial passage closed at one end, means providing aby-pass valve seat in said passage, a by-pass valve for said seat andresilient means heldunder compression between said closed end of saidpassage and said by-pass valve to'hold said-valve,

closed.

2. In a valve assembly, a valve housing havseat, and resilient meansbetween said closed end' and said by-pass valve urging said by-passvalve into seating engagement, said member, by-pass valve and resilientmeans being removable through said larger open end of said valve.

3. In a relief valve assembly, a valve housing open at one end, a covertherefor, a diaphragm peripherally clamped between said housing andcover, a hollow relief valve mounted in said housing, a memberpositioned in said valve for transmitting pressure from said diaphragmto close said valve and also providing a lay-pass valve seat, a, by-passvalve for seating thereagainst and a spring urging said by-pass valveagainst said seat, said valve, member, by-pass valve and spring beingcapable of assembly by simply dropping the same into place through theopen end of said housing in the proper order.

4. In a relief valve assembly, a valve housing open at one end, a covertherefor, a diaphragm peripherally clamped between said housing andcover, a hollow relief valve mounted in said hous ing and havingextensions for slidably guiding the same for movement therein, a memberfreely seated in said valve for transmitting pressure from saiddiaphragm to close said valve and also providing a by-pass valve seat, aby-pass valve for seating thereagainst and a spring urging said by-passvalve against said seat, said valve, member, by-pass valve and springbeing capable of assembly by simply dropping the same into place throughthe open end of said housing in the proper order.

5. In a relief valve assembly, an open-ended valve housing havingaxially spaced coaxial bores and an intermediate annular partitionproviding a valveseat, a hollow internally shouldered valve resting onsaid seat when closed and having extensions slidably guided in saidbores, an annular member positioned in said valve to rest on theinternal shoulder thereof and provide a by-pass valve seat, a by-passvalve therefor, a spring urging said by-pass valve against said seat,and a peripherally held diaphragm closing one end of said valve housingand responsive to pressures exerted thereon to transmitforces throughsaid annular member tending to hold said relief valve against its seat.

6. In a relief valve assembly, an open ended valve housing havingcoaxial cylindrical bores extending from said ends and an intermediateannular portion providing a relief valve seat,

\ a hollow, ported relief valve having a closed end slidably fitting inone of said bores and an open end slidably fitting in the other of saidbores a ported annular member interfitted within said relief valve toprovide a by-pass valve seat, a by pass valve therefor, and a springconfined under compression between the closed end of said relief valveand said by-pass valve to urge the latter into closed position.

7. In a reliefvalve assembly, an open ended valve housing having coaxialcylindrical bores extending from said ends and an intermediate annularportion providing a relief valve seat, a hollow, ported relief valvehaving a closed end slidably fitting in one of said bores and an openend slidably fitting in the other of said bores, a ported annular memberinterfitted within said relief valve to provide a by-pass valve seat, abypass valve therefor, a spring confined under compression between theclosed end of said relief valve and said by-pass valve to urge thelatter into closed position, and a peripherally held diaphragm closing"the other of said bores and responsive to pressures exerted thereon totransmit forces through said annular member tending to hold said reliefvalve against its seat.

8. In a valve assembly, a hollow valve open at one end and closed at theother and provided with an external seating surface, said ends havingcylindrical external guiding surfaces, said valve being further providedwith an 'intermediate internal aimular shoulder and the wall of saidvalve being ported above and below said shoulder, a ported member seatedon said shoul- 'der and formed with a dependent cylindrical portionproviding an annular by-pass valve seat, a by-pass valve for said seatand a spring positioned in said closed valve end for urging said bypassvalve against its seat.

9. A valve element comprising a cup-shaped member having externalcylindrical guiding surfaces. adjacent the upper open end and the lowerclosed end thereof and having an intermediate external seating surface,the wall of said member being ported above and below said seatingsurface.

12). A relief and by-pass valve assembly, com- I prising a cup-shapedrelief valve having external guiding surfaces and an intermediateexternal seating surface, the wall of said valve being ported above andbelow said seating surface and being internally offset adjacent saidseating surface, a ported by-pass valve member resting on said offsetwall portion and formed with a dependent portion providing an annularby-pass valve seat, a by-pass valve for said seat and a spring normallyheld under compression between said by-pass valve and the closed end ofsaid cup-shaped relief valve to urge said by-pass valve into seatingrelationship.

11. A fiuid pressure control device including a valve housing comprisinga wall separating a high pressure cavity and alow pressure cavity andproviding a relief valve seatbore, a wall on the high pressure sideproviding a dash-pot cylinder bore, a wall on the low pressure sideproviding a guide bore, said-bores being coaxial, a relief valve fittingsaid boresand provided with an axial port and with lateral ports settingcommunication between said high pressure cavity and said low pressurecavity, a by-pass valve seat and a by-pass valve arranged in said axialport, said by-pass valve provided with axial and radial ports settingcommunication between said high pressure'cavity and said low pressurecavity, a spring pressing said by-pass valve against said by-pass valveseat, a flexible diaphragm having effective area substantially equal tosaid relief valve seat, a cover clamping said diaphragm in fluid tightmanner on said valve housing on said low pressure cavity, said coverproviding a top wall with an axial bore and a side wall with a verticalgroove, an adjusting screw provided with a flange and lodged in saidaxial bore, a Washer provided with a radial finger fitting into saidgroove to prevent rotation of said washer and provided also with acentral threaded hole fitting the spring a relatively large circularopening providing communication between said chambers, the margin ofsaid opening constituting a valve seat, a

bore associated with said upper chamber and a bore associated with saidlower chamber, said bores and said opening being coaxial, a valve bodyhaving a pair of concentric cylindrical surfaces each adapted for axialreciprocation in one of said bores and including a valve surface adaptedto cooperate with said valve seat whereby to close said opening, saidvalve body being provided with a relatively large axial openingtherethrough whereby to permit communication between said chambers whensaid valve and seat are in engagement, a second valve serving to controlcommunication through the axial opening in said valve body and openingin the opposite direction with reference to said first valve, flexiblepressure responsive means and spring means operative to press saidvfirst valve against said seat, and a spring tending to keep said secondvalve closed. I

13. A fluid flow control device for a pump including a valvehousing'providing an upper and a lower chamber, the upper chamber beingadapted to be connected to the suction side of the pump and the lowerchamber being adapted to be connected to the pressure side of said pump,said chambers being separated by a partition provided with an openingforming a communication between said chambers, the margin of saidopening constituting a relief valve seat, a relief valve arranged insaid opening and including a valve surface adapted to cooperate withsaid valve seatto close and open said opening in said partition, saidrelief valve also including an axial'by-pass opening therethrough topermit communication between said chambers, the margin of said latteropening constituting a by-pass valve seat, a by-pass valve arranged tdclose said by-pass opening or to open said by-pass opening, reliefspring means tend= ing to close said relief valve, by-pass spring meanstending to close said by-pass valve, and a pressure responsive diaphragmhaving an effective area substantially equal to the area of said reliefvalve, said diaphragm being placed between said relief valve and saidrelief spring,

said relief valve fitting said bore whereby to provide a dash-pot actionfor dampening axial vibrations of'said relief valve.

15. The structure recited in claim 13 in combination with means in saidvalve housing providing a cylindrical bore, an extension of said reliefvalve fitting said bore, said extension being provided with an axialdash-pot port providing a valve seat, a dash-pot valve member closingsaid valve seat, and spring means to keep said dash pot valve closed.

16. A fluid control device including a valve housing having a suctionside chamber and a pressure side chamber, a partition separating saidchambers and provided with a circular opening setting communicationbetween said.

' chambers, the margin of said opening constitutmg a valve seat, saidhousing also providing a suction side cylindrical bore and a pressureside cylindrical bore, said bores and said opening being coaxial, arelief valve member through said opening and said bores, said reliefvalve member provided with a relief valve surface adapted to collaboratewith said relief valve seat whereby to close said opening, a cylindricalsurface fitting into said suction side cylindrical bore, a cylindricalsurface fitting into said pressure side cylindrical bore, a relativelylarge axial opening and radially spaced openings between said axialopening and said chambers whereby to permit communication between saidchambers when said valve and seat are in engagement, said axial openingprovided with a first by-pass valve seat on the suction side, a by-passvalve member lodged in said axial opening and on said first by-passvalve seat, said by-pass valve member also provided with a second axialopening and radial openings whereby to set communication between saidsuction and pressure side chambers and with a second by-pass valve seaton the pressure side, a second by-pass valve member also lodged in saidfirst axial opening and arranged to collaborate with said second by-passvalve seat in closing said second axial opening, a pressure responsivediaphragm resting on said by-pass valve member, and spring meanspressing said diaphragm against said by-pass valve member and therebysaid by-pass valve member against said first by-pass valve seat and saidrelief valve member against said relief valve seat.

17. A fluid fiow control device including a valve housing and a valvelodged in said housing and movable with reference thereto, a pressurerecover for said tension means, tension adjusting whereby said reliefvalve is substantially uninfluenced byvariations of pressure on thesuction side of said pump. Y

14. The structure recited in claim 13in combination with means in saidvalve housing providing a. cylindrical bore, and piston-like means onsponsive diaphragm operatively resting on said valve, tension meansoperatively resting at one end on said valve through said diaphragm, a

means through said cover, said tension means pressing said adjustingmeans against the inside surface of said cover, and outside said coveradditional means operative in further pressing said adjusting meansagainst said cover whereby to provide a fluid tight closure and preventrelative movement of said adjusting means and said cover.

' MICHELE CASERTA.

